August 9 2001. This date is seared in the minds of many US scientists as the most potent symbol of the Bush administration's willingness to put religious-inspired ideology over rationalism and scientific progress.

This was president Bush's cut-off date for federal funding of embryonic stem cell research. Any cell lines created after this date could not benefit from federal funding including the massive $28bn pot handed out annually by the National Institutes of Health.

This is an important step that will accelerate stem cell research in the US. Private and state funding has maintained America's position as the world leader in stem cell research, but the confidence of longer term federal funding for blue skies research will undoubtedly give the field a boost.

It will also leave other countries vulnerable to an exodus of talent as research opportunities in the US spring up. The UK in particular has benefited from Bush's restrictive policies with several talented US researchers choosing to base themselves there and doubtless many more UK scientists deciding not to make the trip across the pond.

The change can only help scientists' understanding of how human tissues develop and bring forward treatments for so far intractable diseases such as Alzheimer's and Parkinson's. But it won't change anything overnight. Research is a long game and it will be years or decades before this decision bears fruit.

More importantly, it sends an early message about how this administration values research, evidence and rational argument. Many in the scientific community have spent the last eight years fighting ideological obstructions to their work.

Public health researchers under Bush were stopped from attending conferences or promoting evidence for the effectiveness of condoms against the Aids pandemic; scientific advice on climate change was doctored by administration lackeys to play down the causal role human activities; and expert advisory committees were stacked with ideologues. Even the president's science adviser was kicked out of the White House to a place in the Washington bureaucracy where he could safely be ignored. Obama has pledged to restore the position's previous authority.

Repealing Bush's stem cell law is an easy and obvious change to make. Much more significant though will be whether Obama's administration brings sound scientific advice and a thoughtful rationalist approach back into the Oval Office. The consequences of that go way beyond US science.